Bogwood, or "morta," which appears several times in Ulysses as "bogoak," is wood that has been buried in peat bogs for millennia. Anaerobic conditions preserve the wood, and its tannins combine with iron dissolved in the acidic water to stain it darker and darker as time goes on, in a process that eventually leads to pure blackness and coal-like petrification.
Irish bogs are one of the few places on the planet conducive to the formation of bogwood, whose aesthetic qualities combine with its rarity to make it as highly prized as many tropical hardwoods. It is difficult to work because of unpredictable variations in hardness, but pipe-makers accept the challenge because the high mineral content makes for wood that will not burn easily, and low tannins leave the tobacco's flavors unadulterated. Carpenters and woodworking artists also seek out the material.
In Proteus Richie and Sara Goulding sleep under a picture that is encased in a "bogoak frame." The embroideries on the Citizen's handkerchief in Cyclops depict a "bogoak sceptre." And in Circe Bloom appears "In caubeen with clay pipe stuck in the band, dusty brogues, an emigrant's red handkerchief bundle in his hand, leading a black bogoak pig by a sugaun, with a smile in his eye."